Enhancing the Acceptor Character of Conjugated Organoborane Macrocycles: A Highly Electron‐Deficient Hexaboracyclophane

Abstract

We introduce an ew boron-doped cyclophane,t he hexabora[1 6 ]cyclophane B6-F Mes,i nw hich six tricoordinate borane moieties alternate with short conjugated p-phenylene linkers.E xocyclic 2,4,6-tris(trifluoromethyl)phenyl ( F Mes) groups serve not only to further withdraw electron density but at the same time sterically shield the boron atoms,resulting in am acrocycle that is both highly electron-deficient and stable.The optical and electronic properties are compared with those of related linear oligomers and the electronic structure is further evaluated by computational methods.T he studies uncover unique properties of B6-F Mes,i ncluding al ow-lying and extensively delocalized LUMO and aw ide HOMO-LUMO gap,w hicha rise from the combination of ac yclic psystem, strong electronic communication between the closely spaced borons,a nd the attachment of electron-deficient pendent groups.T he binding of small anions to the electrondeficient macrocycle and molecular model compounds is investigated and emissive exciplexes are detected in aromatic solvents.

Scalable, Durable, and Recyclable Metal‐Free Catalysts for Highly Efficient Conversion of CO2 to Cyclic Carbonates

“…The direct evidence for the ring‐opening of PO by 1 c ( 1 c /PO=1/10, mole ratio) was provided in Figure 4 c, wherein a strong and sharp boron nucleus resonance at −1.32 ppm (fwhm=317 Hz) was clearly observed, which could verify that the intermediate of II involved a tetra‐coordinated boron structure [22] . The nucleophilic attack of 1 c at less steric site of PO was confirmed by the detection of the corresponding resultant iodoalcohol (Figure S11).…”

Polycationic Redox‐Active Cyclophanes with Integrated Electron‐Rich Diboron Units

“…[8] Jäkle et al synthesized several boracyclophanes with interesting optical and redox properties. [9][10][11][12][13][14] One example is sketched in Figure 1. In these compounds, the B III atoms are Lewis-acidic sites and act as electron-acceptors.…”

Electron‐Deficient Conjugated Materials via p–π* Conjugation with Boron: Extending Monomers to Oligomers, Macrocycles, and Polymers

“…Due to the presence of multiple electron‐deficient organoborane moieties, this macrocycle is expected to exhibit high affinity for electron‐rich substrates. In this vein, the Jäkle group very recently introduced a more highly electron‐deficient hexabora[1 6 ]cyclophane ( 16 ) in which the shorter phenylene linker and electron‐deficient exocyclic FMes groups further enhance the acceptor character [40] . As a consequence, the LUMO of 16 is further decreased relative to that of 15 , and the splitting of the reduction waves in the cyclic voltammogram is greatly enhanced.…”